Hand, electric and pneumatic tool drivers are well known. Although twist drills are the most common tools on such drivers, the tools may also comprise screw drivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tool shanks may be of varying diameter or of polygonal cross section, the device is usually provided with a chuck adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore.
A variety of chucks have been developed in the art. In an oblique jawed chuck, a chuck body includes three passageways disposed approximately 120 degrees apart from each other. The passageways are configured so that their center lines meet at a point along the chuck axis forward of the chuck. The passageways constrain three jaws that are moveable in the passageways to grip a cylindrical or polygonal tool shank displaced approximately along the chuck center axis. The chuck includes a nut that rotates about the chuck center and that engages threads on the jaws so that rotation of the nut moves the jaws in either direction within the passageways. The body is attached to the drive shaft of a driver and is configured so that rotation of the body in one direction with respect to the nut forces the jaws into gripping relationship with the tool shank, while rotation in the opposite direction releases the gripping relationship. The chuck may be keyless if it is rotated by hand.
Various configurations of keyless chucks are known in the art and are desirable for a variety of applications. In the case of a two sleeve chuck, the front sleeve is preferably rotationally coupled to the nut and the rear sleeve is rotationally coupled to the chuck body. Thus, rotation of the front sleeve relative to the rear sleeve causes the jaws to move within the chuck body in either the opening or closing direction, depending on the direction of relative rotation. In a single sleeve design, however, rotation of the chuck body relative to the single sleeve, and therefore the nut, is generally accomplished by actuating the drill unit while an operator holds the sleeve. It is also known to provide a sleeve on the driver housing that is rotationally fixed to, but axially moveable with respect to, the housing. This sleeve is moveable into engagement with the chuck sleeve so that the sliding sleeve rotationally fixes the chuck sleeve and the nut to the driver housing. Upon activation of the driver, therefore, the driven spindle rotates the chuck body relative to the rotationally fixed sleeve and nut, thereby opening or closing the chuck depending on the spindle's rotational direction.